How NSA Hacked North Korean Hackers

The U.S. government's attribution of the Sony Pictures Entertainment hack attack to North Korea stems, in part, from the U.S. National Security Agency having infected a significant number of North Korean PCs with malware, which the intelligence agency has been using to monitor the country's hacking force.

So says The New York Times, which bases its report, in part, on interviews with unnamed former U.S. and foreign officials, as well as a newly leaked NSA document. The document, published Jan. 17 by German newsmagazine Der Spiegel - and obtained via former NSA contractor Edward Snowden - details how the NSA worked with South Korea - and other allies - to infiltrate North Korea. The agency reportedly infiltrated at least some of these computers by first exploiting systems in China and Malaysia that help manage and administer North Korea's connection to the Internet.

According to the Times report, the hacked computers have given the NSA an "early warning radar" against attacks launched by the Pyongyang-based government of North Korea. Related intelligence gathered by the NSA also reportedly helped convince President Obama that North Korea was behind the Sony Pictures hack.

North Korea's Reconnaissance General Bureau intelligence service, as well as its Bureau 121 hacking unit, control the vast majority of the country's 6,000-strong hacking force, some of which operates from China, according to news reports.

Fourth Party Collection

Some of the evidence of the NSA's ability to monitor North Korean systems comes from a leaked NSA document, which appears to be a transcript of an internal NSA question-and-answer discussion that's marked "top secret" and is restricted to the U.S. and its Five Eyes spying program partners: Australia, Canada, New Zealand and the United Kingdom. The document refers to the NSA's practice of "fourth party collection," which involves hacking into someone else's hack, according to a Der Spiegel report.

The document relays an episode that involves North Korea: "We found a few instances where there were NK [North Korea] officials with SK [South Korea] implants [malware] on their boxes, so we got on the exfil [data exfiltration] points, and sucked back the data," the document reads.

Der Spiegel reports that this practice, which is employed by the NSA's Tailored Access Operations team, has been used extensively to undermine many hack attacks emanating from Russia and China and has allowed the NSA to obtain the source code for some Chinese malware tools.

But some attacks against U.S. systems did succeed, and one leaked NSA document says that as of several years ago, 30,000 separate attacks had been detected against U.S. Defense Department systems, 1,600 systems had been hacked, and related "damage assessment and network repair" costs had exceeded $100 million.

The NSA document also discloses that South Korea in recent years has begun attempting to hack into some U.S. government systems.

The FBI has previously said that its attribution of the Sony Pictures hack was based in part on intelligence shared by the NSA, although that attribution did not single out the North Korean government, thus leaving open the possibility that pro-Pyongyang hackers or even mercenaries may have also been involved.

The Role of Botnets

On the attribution front, meanwhile, documents newly published by Der Spiegel - and leaked by Snowden - have detailed an NSA program, code-named "Defiantwarrior," which involves the NSA using infected nodes - or zombies - in a botnet. When such nodes are traced to U.S. computers, the FBI reportedly uses the information to help shut down those parts of the botnet. But when nodes are discovered on computers in countries outside the Five Eyes program, the NSA - according to the leaked documents - may use these to launch attacks against targets. While such attacks might be traced back to the botnet node, this practice reportedly helps the agency launch attacks that are difficult - if not impossible - to attribute back to the NSA.

New Snowden docs claim that when FBI takes down botnets, control of interesting foreign computers is given to the NSA pic.twitter.com/qSkxMcDOZ8

Did NSA Keep Quiet?

The report that the NSA had hacked into many of the systems employed by the North Korean military, and was monitoring them, has prompted information security experts to question whether the agency knew about the Sony Pictures hack and failed to stop it.

"If the NSA were secretly spying so comprehensively on the networks used by North Korea's hackers, how come they didn't warn Sony Pictures?" asks independent security expert Graham Cluley in a blog post.

If the NSA did detect signs of the Sony hack planning, reconnaissance and actual attack unfolding, however, then it might have declined to warn the television and movie studio to avoid compromising that monitoring ability, says Europol cybersecurity adviser Alan Woodward, who's a visiting computing professor at the University of Surrey in England. Similar questions have been raised in the past, for example, over the World War II bombing of Coventry, England, by the Germans, and why - if the British had cracked the Nazis' secret Enigma codes - the U.K. government didn't evacuate the city.

@gcluley I wonder if this was classic case of protecting your source at cost of someone else damage - like Enigma and bombing of Coventry.

Another outstanding question is the extent to which the leadership of North Korea suspected - or knew - that their computer systems may have been infiltrated by foreign intelligence services. "Presumably, the cat is now out of the bag," Cluley says. "These news stories may take some of the heat off the [United] States from some of those in the IT security world who were skeptical about the claims of North Korean involvement, but it also tips off North Korea that it may want to be a little more careful about its own computer security."

About the Author

Schwartz is an award-winning journalist with two decades of experience in magazines, newspapers and electronic media. He has covered the information security and privacy sector throughout his career. Before joining Information Security Media Group in 2014, where he now serves as the executive editor, DataBreachToday and for European news coverage, Schwartz was the information security beat reporter for InformationWeek and a frequent contributor to DarkReading, among other publications. He lives in Scotland.

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